Many methods are now available to be used in the treatment of cancer. Despite considerable advances, however, treatments for many cancers are inadequate for a number of reasons.
There are still cancers which simply do not respond or respond poorly to treatments are currently available. Patients with treatable cancers must often undergo chemotherapy with drugs that cause severe side effects. Few of these drugs can be used orally. Perhaps the most serious problem associated with cancer chemotherapy is the development of multi-drug resistance by many tumors. For example, many tumors which initially respond positively to an anti-cancer therapy by decreasing in size or even going into remission often develop resistance to the drug. Tumors that have developed resistance to more than one drug are said to be a “multi-drug resistant”. There is little that can be done to halt or retard further progression of the disease, once a patient's cancer has become multi-drug resistant.
There is therefore still a need for new drugs which overcome one or more of the aforementioned shortcomings of drugs currently used in the treatment of cancer. Desirable properties of new anti-cancer drugs therefore include efficacy against tumors that are currently untreatable or poorly treatable, efficacy against multi-drug resistant tumors, oral bioavailability and/or reduced side effects.